1. Field of the Invention
The present invention relates to the treatment of residue materials containing rare earth and cobalt values, and, more especially, to the recovery of samarium and cobalt values from waste products resulting from the production of magnets.
2. Description of the Prior Art
At the present time, the development of alloys based on the rare earths, in particular samarium/cobalt alloys, as permanent magnets, is of significant interest.
The rare earths, in particular samarium, are expensive raw materials; it is thus important to recover these values from all of the residues of the manufacture of magnets.
Different processes are known to this art for the treatment of such residues. Some of these operate by selective precipitation after the acid decomposition of the residue (JP-A 61/000533, JP-A 61/000532, JP-A 54/089904), while others treat the solution obtained after the acid attack, by electrolysis, to recover the cobalt (JP-A 59/067384).
In JP-A 60/122718, a process is described for the recovery of samarium from a particular residue by dissolving such residue in an organic phase containing an extraction agent, such as a dialkylphosphoric acid, in particular di(2-ethylhexyl) phosphoric acid, and then extracting the samarium from the organic phase into an aqueous phase, by means of a concentrated acid solution having a normality ranging from 1 to 5N, preferably from 2 to 5N. The process has the disadvantage of a difficult back-extraction of the samarium values, at the time of the regeneration of the solvent of extraction, giving rise to high operating costs.